In view of the category of the portable low-end type in particular, the primary object of the present invention is to provide the technology for implementing video or digital cameras whose depth dimension is reduced while high image quality is ensured, and which are easy to handle.
The gravest bottleneck in diminishing the depth dimension of cameras is the thickness of an optical system, especially a zoom lens system from the surface located nearest to its object side to an image pickup plane. Recent technologies for slimming down cameras rely primarily on a collapsible lens mount that allows the optical system to be taken out of a camera body for phototaking and received therein for carrying. Typical examples of the zoom lens system so far known to be well fit for electronic image pickup devices and have satisfactory image-formation performance inclusive of zoom ratio, angle of view and F-number are disclosed in JP-A's 11-287953, 2000-267009 and 2000-275520.